Production of ketones



aiented Aug. 15, 1944 rnonucrron or KETONES Alva C. Byrns, Palos VerdesEstates, CaliL; assign- .or to Union Oil Company of California, LosAngeles, Calii-'.,a corporation of California No Drawing." ApplicationMay 6,1941, Serial No. 392,095

9 Claims. -(Cl. 260+593) copious evolution of hydrogen chloride as theThis invention relates to processes for producing ketones and relatedcompounds and is a continuation in part of my copending application,Serial No. 322,341, filed March 5, 1940; The invention further residesin the production of new and'novel ketones of distinctive odor useful asreaction progresses. Furthermore, under relatively mild reactionconditions, mild catalysts,

such as for example, anhydrous zincchloride, will solvents, chemicalintermediates and as ingredi- I ents in perfumes.

In a more specific sense, the invention is concerned with processes forselectively reacting organic acid anhydrides with olefins, preferably inthe presence of a mild catalytic agent, such as,

for example, anhydrous zinc chloride, to prowould react with organicacid chlorides in the presence of anhydrous aluminum chloride to producechloroketones. Nitzescu and Gavat (Annalen, vol. 519, Page 260, 1935)observed that propylene would react with acetyl chloride in the presenceof a large excess of anhydrous aluminum chloride to produce achloroketone which could be subsequently condensed with benzene to forma phenyl'pentanone' as shown by the following equation:

CHa

cn-cm-co-cm CIHI I Likewise, it has been shown by Ada-ms and Noller(Organic synthesis," collective vol. I, page 105, John; Wiley and Sons,1932) that acetic anhydride will react with benzene in the presence ofanhydrous aluminum chloride to form acetophenone, an aralkyl ketone. Inorder to obtain maximum yields of acetophenone it is necessary to use atleast two mols of aluminum chloride for each mol of acetic anhydride.Groggins, Nagel and Stirton (Industrial and Engineering Chemistry, vol.26, page 1317, 1934) have demon-' strated that the reaction proceedsthrough the formation of acetyl chloride from acetic anhydride and partof the aluminum chloride, and subsequent reaction of the acetyl chloridewith the benzene in a manner typical of the well known Friedel andCrafts reaction. It is to be particularly noted in the last example thatthere is a not cause the reaction to occur, possibly due to inability toform the acid chloride from the anhydride. In typical Friedel and Craftsreactions and variations thereof, such as the two above describedexamples, it is usually necessary to employ at least one, and ordinarilytwo or more,'mols of catalyst per mol of reactant in order to realize amaximum yield of the desired product. The catalyst reacts chemicallywith the reactants and is ordinarily not readily recoverable.

It is an object of my invention to provide a process for selectivelyreacting an olefin with an organic acid anhydride to produce ketoniccompounds. It is. another object to produce ketonic compounds byselectively reacting an acid anhyeral equations:

(1) CDHI R-CO-O-CO-R Aliphatic Acid anhydride olefin Callas-100R RCOOHKetone Carboxylic acid (2) 0.1115 RC0-000R Cyclo 'Acid anhydride oleilnC-Hn-aCOR RCOOH Ketone acid hydrocarbon radical. The hydrocarbonradicals present in the acid anhydride may be the same, as they are inacetic anhydride,

or they may be different as in a mixed acid anhydride, such asCHs-CO-O-CMH: or

Carborylic they may be combined in one radical soas to give a cyclicstructure, such as is present for example, in phthalic anhydride andsuccinic anhydride. In the case of acid anhydrides of the latter type,the reaction results in the formation of a keto acid as shown in thefollowing exemplary equation:

C 0C 4H7 0 C4Ha i C O OH C O Phthalic anhydride Butylene Keto acidEquation 1 above, represents the combination of an olefin of thealiphatic or ethylene series of hydrocarbons with an organic acidanhydride to form a ketone and an organic acid. Although I have foundthat any olefin of the aliphatic series of hydrocarbons will react withan organic acid anhydride to produce a ketoniccompound undersufficiently rigorous conditions, I have further discovered that olefinshaving branched carbon chains and especially those having the followingconfigurations or structures which are converted into the followingconfigurations under the conditions of the reaction, are particularlyreactive and will combine with an organic acid anhydride underrelatively mild reaction conditions.

In the above structural formulas, R represents either a hydrogen atom ora hydrocarbon radical and the various Rs may be the same or different.

'It is one of the objects of the present invention to-provide a processfor producing ketones under relatively mild reaction conditions byreacting organic acid anhydrides with olefins having the structuralconfigurations 'RzC= C(CR3)CRa and R2C(CR3) CH=CR2 and preferably thosehaving the structural configuration CH2=C(CRa) CR3 where R representseither a hydrogen atom or a hydrocarbon radical and preferably eitherhydrogen or an alkyl hydrocarbon radical and the various Rs may be thesame or different.

Equation 2, above, represents the combination of a cyclo-olefin with anacid anhydride to produce a ketonic compound. Cyclic olefins, such asfor example, cyclohexene, cyclopentene and methyl cyclohexene, appear tocondense with acid anhydrides to form ketones as readily as do thebranched chain olefins of the aliphatic hydrocarbon series. Therefore,in general, the same reaction conditions and catalysts which causeformation'of ketonic compounds from branched chain olefins of thealiphatic hydrocarbon series and acid anhydrides will likewise lead tothe formation of ketones by the interaction of cyclo-olefins and organicacid anhydrides.

The above discussion has mentioned various pure compounds withoutconsideration of the source from which such olefins may be derived. Forexample, as is well known in the art, diisobutylene is obtained byselective polymerization of isobutylenes in the presence of a catalyst,such as sulfuric acid. Other olefins may be obtained by dehydration ofsuitable branched chain alcohols, or by removal of hydrogen halide fromalkyl halides. Similar olefins are obtained'by polymerization of lowermolecular weight olefins, such as the mixture of propenes, butenes andpentenes obtained in the cracking of petroleum. One such mixture isknown as "mixed octenes,

and is obtained by non-selective polymerization of the butene-isobutenefraction. The fraction known as polymer gasoline", produced byphosphoric acid polymerization of cracking plant gases, has also beenfound to be a suitable source of olefins. This fraction may be reactedwith an organic acid anhydride to produce a ketone fraction having awide boiling range which may be fractionated to obtain relatively pureketones. The preferred method involves distilling such a polymergasoline into a number of narrow boiling range fractions which may bereacted with the organic acid anhydride to produce ketone fractionshaving relatively narrow boiling ranges compared to those obtained whenthe unfractionated polymer gasoline is used. In general, it is preferredto use normally liquid olefins having five carbon atoms or more, sincepressure does not have to be applied to the reaction system.Furthermore, the ketones obtained from olefins containing five carbonatoms or'more have been found to possess greater value in the arts.

I have further discovered that the reaction-is most readily carried outwith those organic acidanhydrides. which are fluid at ordinaryatmospheric temperatures. These compris the acid anhydrides of the lowermolecular weight monocarboxylic acids of. the aliphatic series, such as"acetic anhydride, propionic anhydride, butyric anhydride, etc., and oftne naphthenic acids. The structures of the latter compounds are notdefinitely known but they are believed to be'mono-carboxylic acidscontaining one or more naphthenic hydrocarbon rings, the rings beingeither mono or hetero-cyclic. In many of the industrial applications ofketones, it appears that methyl ketones, that is, those possessing theCHa -CO group, are particularly valuable. Such ketones can be obtainedby the processes of the present invention by employing acetic anhydrideas the acid anhydride to be reacted with'the olefin, and this anhydrideis, therefore, to be particularly preferred. Where it isdesired to,react those acid anhvdrides whichare solid. at the usual atmos.

pheric temperatures it is ordinarily necessary to employan inert solventas the reaction medium or conduct the reaction at asufliciently elevatedtemperature tomelt the acid anhydride.

In addition to the foregoing, I have observed that if an olefin,particularly a branched .chain olefin of the types describedhereinabove, such as for example, di-isobutylene, is mixed atatmospheric temperature with an organic acid anhydride, there is littleor no evidence that any reaction occurs and in fact it is possible toseparate the olefin fromthe anhydride substantially unchanged. However,if a quantity i a mild catalyst, such as for example, anhydrous zincchloride, is added to the mixture of olefin and acid anhydride at roomtemperature, it is immediately apparent that a reaction is occurring asis evidenced by the evolution of considerable heat and a marked changein the odor of the material. Closer examination of the mass reveals thata ketone between wide limits, but it has been found that the optimumyield of ketone-is obtained with only about 0.2 mol of sulfuric acid permol of acid anhy'dride. Temperatures not appreciably higher than 100 F.are preferred, since side reactions such as sulfonation are minimized,but temperatures as high as the boiling point of the reaction v mixturehave been used.

If anhydrous aluminum chloride is added to a mixture of olefin and acidanhydride at room temperature a reaction occurs accompanied withevolution of hydrogen chloride, but the resultant 1 product appears tobe a mixture of many different compounds boiling over a wide range oftempera:- tures with no particular compound being formed in relativelylarge amount. This is readily understandable in view of the known highactivity of aluminum chloride and its ability to rupture as well ascause the formation of carbon to carbon bonds. e

I 3 perature of the mass is preferably maintained in the neighborhood of100 F. throughout the experiment and inany event it is not to exceed'200" F. since at higher temperatures acetic anhydride appears todecompose to a tarry mass in the presence of zinc chloride. Reactionwill occur at temperatures considerably below 100 F. but the formationof the ketone is slow and intimate contacting of the aceticanhydride-zinc chloride mix ture with the olefin is more difficult toobtain because of the decreased fluidity of the reaction mass.

After most of the zinc chloride'had dissolved in the acetic anlnrdrideand the temperature had been adjusted to approximately 100 F., 150milliliters of commercial di-isobutylene (equivalent to 1 mol) was addedover a period of two hours and intimately mixed with the aceticanhydridezinc chloride complex. Considerable heat is evolved during thereaction and it was necessary to 'cool the reaction mixture in order tomaintain the temperature in the neighborhood of 100 F.

Commercial di-isobutylene is a mixture of two principal isomers:2,4,4-trimethyl pentene-l and 2,4,4-trimethyl pentene-2, comprisingabout and 20% of the commercial product, respectively.

After 'all of the di-isobutylene has been added,

the mass was agitated for an additional two hours in order to allowtimefor the reaction to complete itself and 300-400 milliliters of waterwere ketone. In passing it should particularly. noted that'at no stagein the process was there any evidence of the formation of hydrogen chlo-It is an additional obicct of the'present invention to produce ketonesby reacting an olefin, preferably a branched chain olefin having one ofthe configurations described hereinabove, with an organic acidanhydride, preferably derived from one of the lower molecular weightmonocarboxylic acids, said reaction being conducted in the presence of amild catalytic agent such as anhydrous zinc chloride and at atmosphericor somewhat elevated temperatures.

Other features, advantages and objects of the present invention willbecome apparent to those skilled in the art from the following specificexamples: i

Exempted 4 -mass,, heat being evolved and a complete! the two compoundspossibl being formed. The temthen added into the reaction vessel. Thiscaused a separation of the reaction mixture into two liquid. phases; alower aqueous phase containing zinc chloride andflacetic acid and anupper brownish-colored phase constituting the crude ride, thusdistinguishing this reaction from the usual Friedel-Crafts reactions.

The two phases were.. separated,and the upper washed twice with waterand finally treated with dilute sodium carbonate solution to remove thelast traces of acetic acid. The ketone formed is at most only veryslightly soluble in water, and,

millilters, was finally'fractionated under reduced pressure to produce apractically colorless mobile pleasant odor.

liquid of narrow boiling range and distinctive The crude ketone can befractionated at atmospheric pressure but the resultant material-isyellowish in color, possibly due to the presence of small amounts ofdecompositionproducts. Steam distillation of the crude ketone can beresorted to if desired.

The pure ketone constituted approximately of the recovered crudeketonephase, the remaining 15% being principally unreacteddi-isobutylenetogetherwith asnrali amount-cf high;-boilingimaterial;possiblytetraisobutylene.

.added an excess of sodium acetate.

properties: v

Specific gravity, 60/60 F ;j. 0.848 Refractive iflrlPY 1.452 Boilingpoint, F. (uncorn) 375 Boiling point, F; 18 mm. (uncorr.) 173Quantitative analysis of the pure ketone indicated that it had thefollowing percentage composition: carbon 77.60%, hydrogen 11.92%, andoxygen 10.40%. These values are in good agreement with those of theexpected empirical formula CioHmO which has the following percentagecomposition: carbon 77.87%, hydrogen 11.76% and oxygen 10.37%. Theseresults indicate that the reaction takes place in accordance with thefollowing equation:

Acetic Ketone Acetic acid anhydride Di-isobutylene It is characteristicof ketones in general to react with semi-carbazide, NI-I2-CO-NH-HN2, toform semi-carbazones,

the latter in general being easily purified solids, the physicalcharacteristics of which can be used to identify the ketone. The narrowboiling fraction obtained from the distillationof the crude ketone layerwas added to an aqueous solution of pure ketone exhibited the followingphysical proves that the structure of the main component has thefollowing configuration; i .1

cent and after making allowance for unreacted di-isobutylene recovered,it is evident that there is an appreciable amount of di-isobutyleneunaccounted for. The aqueous phase separated from the crude ketone afterhydrolysis of the reaction product was cooled to a'temperature ofsemi-carbazide hydrochloride to which had been A solid.precipitate'indica'ting the formation of the semicarbazone anddemonstrating that the compound obtained is a ketone. The melting pointof the separated and purified semi-carbazone is 334-336 F. (unc'orr).

Another reaction which is characteristic of the CHsCO group orgroups'which will readily yield this configuration under the conditionsof the test is the Haloform Reaction, an improved modification of whichis described by Fuson and Tullock, Journal of the American ChemicalSociety, vol. 56, page 1638 (1934). The test depends upon the reactionof sodium hypoiodite with compounds containing the CHaCO group to formiodoform. The narrow boiling fraction obtained from the distillation of.the crude ketone was tested in accordance with the description ofapproximately 35 F. A crystalline solid of slightly yellowish colorprecipitated and was separated from the supernatant liquidby'filtration. Precipitation of the crystalline material can likewise beaccomplished through concentration of the solution by partialevaporation. This crystal line product appears to be a complexcomprising zinc chloride and a ketone having fourteen carbon atoms. Thiscrystalline complex reacts with hydroxylamine to form a crystallineoxime with I the liberation of zinc chloride and with dilute Fuson andTullock, noted above, and iodoform positively identified in the reactionproducts.

This evidence was taken in conjunction with that forthe formation of asemi-carbazone definitely indicates that the compound isolated containsa CHaCO group and therefore has the formula The structure of unsaturatedcompounds of the type prepared as described above is best determined bythe ozonolysis, followed by decomposition of the ozonide 'andidentification of the decomposition products. When this ketone was sotreated, according to standard procedure; only methyl neopentyl ketoneand methyl glyoxal could be isolated in measurable quantities. Thisammonia to form an imine'boiling at l14.5 C. at-a pressure of 25 mm. Ofparticular interest is the fact that an aqueous solution of thecrystalline complex reacts readily with aniline at room.

temperature to form a Schifis base type of compound.

Example 2 The yields of ketones realizable from any given set ofreactants is apparently markedly affected by the order in which the,reactants are added a to the reaction vessel. In an experimentcomparable to Example 1, 4350 grams of anhydrous zinc chloride(technical, 94% 'pure) was mixed with 4600 milliliters of commercialdiisobutylene and 3150 milliliters of acetic anhydride subsequentlyadded slowly to the mixture. After a1- lowing sufficient time for thereaction to complete itself,'the mixture was hydrolyzed with water inthe manner previously described in Example 1, above. Approximately 3870millilitersv of crude ketone was obtained and on fractionation of the'material, it was found that there was no unreacteddi-isobutylene,present, the product being comprised essentially of 50%of the desired ke-' tone and 50% of a high boiling'hydrocarbon, ap-'parently tetraisobutylene. The molal yield of the desired ketone wasonly 26.5%.

Since mild catalysts such as zinc chloride will catalyze thepolymerization of olefins, it appears that the most desirable processfor,- obtaining maximum yleld of ketones comprises admixture of theorganic acid anhydride withthe. catalyst and subsequent slow addition ofthe olefin to the anhydride-catalyst mixture in order toavoid any largeexcess ofunreacted olefinin contact with thecatalyst."

Example 3 Five grams of anhydrous zinc chloride (equivalent to 5 mol)was admixed with 35 milliliters of acetic anhydride (equivalent to Mmol) and 50 milliliters of commercial di-isobutylene (equivalent to mol)subsequently added slowly. After allowing the reaction to completeitself, grams of crystalline complex and 22 milliliters (equivalent to0.12 mol) of ketone. CmHraO, were recovered. This indicates that eachmol of zinc chloride is capable of causing the formation of at leastfour mols of ketone. 1

Example 4 Three milliliters of 94% H2804 was mixed with 30 millilitersof acetic anhydride, the mixture cooled to room temperature and 30milliliters of commercial di-isobutylene added. After allowing one hourfor the reaction to complete itself, the mixture was hydrolyzed withwater and 28 milliliters of a separated ketone phase recovered, of whichapproximately 70% was estimated to be ketone CmHraO.

Example 5 Twenty grams of anhydrous zinc chloride was added to 20milliliters of acetic anhydride and 20 milliliters of cyclohexene(obtained from Eastman) subsequently added. After-hydrolysis of thereaction mixture and fractionation of the ketone layer 18 milliliters ofan oil was obtained which had an odor similar to that of acetophenone.The oil was identified as a ketone.

Example 6 A quantity of 2-ethylhexanol (obtained from Carbide and CarbonChemicals Corporation) was dehydrated to give a mixture of octylenes.This mixture of octylenes 'was reacted with acetic anhydride in thepresence of zinc chloride in the manner outlined in the previousexamples. The hydrolyzate from the reaction mass was comprisedprincipally of ketones.

Example 7 Six hundred milliliters of technical 98% sulfuric acid wasadded to 5660 milliliters (60 mols) of technical acetic anhydride whilecooling in a water bath. Nine thousand three hundred seventy millilitersof techmcal di-isobutylene was added to the mixture during one hourwhile main. taining atemperatureof 68-75IF., after which the mixture wasallowed to stand at 80-85 F. for 18 hours. The product was diluted withwater, washed with dilute sodium hydroxide solution,

- and again with water. A total volume of 8100 milliliters of crudeketone layer was thus obtained. A 4000 milliliter portion 'wasfractionated in a three foot column packed with inch carbon rings,yielding 1700 milliliters of unreacted diisobutylene, 1985 millilitersof ketonc of specific gravity F./60 F.=0.850 and 270 milliliters ofhigher boiling materials still containing some ketone. The yield ofketonewas 37% on the diisobutylene charged, but 68% on the basis of thedi-isobutylene actually consumed.

. Example 8 v A series of experiments were carried out using results ofthese experiments are summarized in the following table:

A sample of polymer gasoline prepared by phosphoric acid polymerizationof cracking plant gases was carefully fractionated in a 60 platecolumnto give a number of narrow boiling frac tions. Representative cutswere then condensed with aceticanhydride, using 0.5 mol of zinc chlorideand 10 milliliters of 98% sulfuric acid per mol of acetic anhydride ascatalysts. The data obtained from these experiments are summarized inthe following table: 1

Yieldi, mol percentt 1 Boning con ensing agen Assumed Cut No. formulapg%t,

' p Sulfuric Zinc acid chloride 01H. i. 200 a 45 C1Hn..-- 207 41 62ClHu--- 232-6 35 39 .CrHn-" 304-12 26 25 1 Based on the assumedhydrocarbon formula.

It was found that almost all of the ketone obtained from out No. 43boiled at 82-85 C. at 40 mm. Hg. pressure, and had a specific gravity 60F./60 F.=0.853. This ketone was ozonized as described for a similarcompound in Example 1 above. Acetaldehyde and a di-ketone, presumablyheptane-2,5-dione were obtained as the principal decomposition productsof the ozonide, indicating that the product obtained in this case hadthe following structure:

o om-orkd-cm-om-d-cm Example 10 In another example the polymer gasolinedescribed in Example 9 was roughly fractionated and two fractionsobtained having boiling points of 194-2'12 I. and 212-230 It, andcomprising 68% of the original gasoline. When these fractions werecondensed with acetic anhydride, using 0.5 mol of zinc chloride ascatalyst, the

lower boiling fraction gave 53% yield of ketones,

while the higher boiling fraction gave 51% yield.

essentially the same technique described in Example 'l, with variationin amount of-sulfuric acid catalyst,. time of reaction and temperature.The

- In the foregoing description it was shown that for each mol of acidanhydride consumed there is produced one mol of acid in conjunction withone mol of ketone. Thisacid represents a byproduct for which it iseconomically desirable to find a use. One method involves reconversionof the acid into anhydride for reuse in the procass. This may be done inseveral ways, as by passing over a dehydrating catalyst and separatingfrom water by the usual means. Another method involves reacting the acidwith ketene (CH2=C=O) vapors which maybe produced by pyrolysis ofacetone. Ketene is known to react rapidly with organic acids, and thismethod is used for commercial production af acetic anhydride and variousmixed'anhydrides (e. g., propionic acetic anhydride). I

A further method of operation as applied to the use of acetic anhydrideeliminates the extra step of synthesizing acetic anhydride as follows:The catalyst is dissolved in the acetic acid recovered from a previousoperation, and the-resulting solution contacted with the olefin to beused. Ketene, or a ketene-methane mixture obtained by pyrolysis ofacetone, is contacted with the acid-olefin-catalyst mixture by suitablemechani-: cal means. Rapid absorption of ketene occurs to form aceticanhydride which reacts with the olefin to produce the desired ketone.The reaction of ketene with acetic acid is much more rapid than thesecond reaction to form ketones. Since acetic acid is regenerated inthis step it is possible to use less than one mol of acetic acid per molof ketene absorbed, and thus in certaincases the acetic acid may beconsidered in the role of an auxiliary catalyst, with ketene as anactual reactant. The extreme case to be considered is that where noadded acetic acid is used, and the reaction is apparently a direct onebetween ketene and olefin in the presence of the catalyst. While such adirect reaction may occur, for example through acetyl sulfuric acid whensulfuric acid is used as a catalyst, I prefer to consider a mechanismwhich involves the above steps. Here it is believed that the ketenereacts with small proportions of water present in the catalyst toproduce a small amount of acetic anhydride. Reaction of the anhydridewith the olefin then regenerates acetic acid as in the previous case. Asa side reaction when ketene is used in place of acetic anhydride,particularly when very little acetic acid is present prior to theintroduction of ketene, there will be some polymerizationto di-ketene.This new product may in turn react with the olefin to produce a limitedamount of 1,3-di-ketones together with the desired mono-ketones, theproportion depending to some extent upon the reaction conditionsemployed, as shown by the examples above.

' an acyclic branched chain olefin in the presence of an acylationcatalyst.

3. A method according to claim 2 in which the olefin is di-isobutylene.

5. A method for the production of a ketone which comprises reacting anacyclic branched chain olefin derived from the polymerization ofcracking plant gases with an organic acid anhy- 'dride in the presenceof an acylation catalyst.

6. A method according to claim 5 in which the a catalyst is concentratedH2SO4. 7. A method for the production of unsaturated ketones whichcomprises reacting a branched chain olefin with an organic acidanhydride in the presence of concentrated sulfuric acid.

8. A method according to claim 7 in which the branched chain olefin hasa structural configuration of the type R R R \E/ n /H R cd=c R 11wherein the various R's represent groups from the class consisting ofhydrogen and hydrocarbon radicals.

9. A method for the production of unsaturated ketones which comprisesreacting an acyclic branched chain olefin and less than an equimolalproportion of an organic acid anhydride in the presence of ketene and anacylation catalyst.

ALVA C. BYBNS.

